Which brings you to an inner diameter of 5mm. From there on, you will need additional adapters and Y splitters - you can easily find these if you look out for fish tank accessories. Another source could be the water cooling stuff for PCs - quite costly, but they have some interesting couplings and other fancy parts…

@pipersw Have a look at these guys (UK Based and if you have trouble getting them to ship to you drop me a msg and I'll see what I can do for you there less than 5kM from me)Hose fittings you can search their site for all sorts of stuff like this.